1. Field of the Invention
The present invention relates generally to the manufacturing of laminated parts from a stack of laminations, and more particularly to a method for forming and stacking individual laminations.
2. Description of the Prior Art
It is well known that certain structures may be formed by the stacking of a series of laminations or laminas. For example, elements of electric motors, solenoids and transformers, such as rotors and stators, may be formed by this process. Typically, the laminas are blanked from continuous strip stock and then stacked and bound together to form the part being manufactured. Another step in the manufacturing process may involve annealing the lamination stack so as to both remove internal stresses within the individual laminas as well as provide an insulating layer on each of the laminations. The stacks are then pressed together into a solid unit so as to form the final machine element.
At least two important considerations in stacking the individual laminations are maintaining the laminas within the stack prior to the final pressing operation, and providing adequate spacing between the laminas while the stack is being annealed and/or insulated. One method for stacking laminations is disclosed in U.S. Pat. No. 4,538,345 issued to Diederichs on Sep. 3, 1985. The method disclosed therein involves the stamping of projections or depressions into the individual laminas and assembling the unit by means of the interlocking projections and depressions prior to the annealing and pressing steps. A minimum axial separation is provided between the individual laminations for the annealing process, and the final stack is assembled in a final pressing operation such that the tabs used to maintain the separation are bent back into their original shape. The separation distance between the individual laminations is achieved by placing tabs in alternate areas on the individual laminations as they are punched or stamped. The alternating displacement in the successive pairs of the laminas in the stack ensure that the tabs in an above lamination come in contact only with a flat part of the next lamina, which has not been bent out.
A second method of ensuring adequate separation between the individual laminations is disclosed in U.S. Pat. No. 5,349,741 to Neuenschwander which issued on Sep. 27, 1994. In this process for forming the plurality of blank laminas, a blanking machine forms dimples in the laminas prior to their stacking, the dimples being located in offset positions relative to adjacent laminations to cause the laminas of the stack to be spaced apart. After the annealing step, the lamina stack is then compressed to bring the laminas into abutting relation to be subsequently manufactured into the rotor or stator cores. The dimples are offset from each other in successive laminas so that the dimples of a succeeding lamina do not fall within a corresponding depression created in the preceding lamina. One method of offsetting the dimples is to arcuately displace every other lamina by rotation of each successive lamina 180.degree. after the dimples have been formed so as to provide the desired offset. An alternative method disclosed of offsetting the dimples is to provide two sets of dimple forming dies alternately actuated by a cam mechanism or the like, resulting in alternately displaced dimples. A separate step forms interlocking portions on the lamina to hold the stack together.
In either case, in order to provide the alternate stamping or rotation, typical prior art methods require relatively complicated machine controllers to ensure that the dimples are offset from each other during the stacking process. Moreover, two separate stamping operations forming two sets of projections may be required: one for providing the offset dimples or tabs, and a second stamping operation to provide interlocking means between individual laminas to ensure that the spaced stack remains assembled during the manufacturing process.
What is needed then is a simplified method for providing an offset between successive laminas in a lamination stack for a machine part so as to ensure adequate separation for a proper annealing process, as well as maintaining the spaced stack in a generally assembled manner during the manufacturing process.
It is therefore an object of the present invention to provide a method of stamping and forming individual laminas to be assembled into a lamination stack such that a minimum separation distance is maintained between the individual laminas.
It is still a further object of the present invention to provide a means and method for joining the individual laminas together during the manufacturing process so as to assemble a spaced pack arrangement.
It is a yet another object of the present invention to simplify the steps necessary in stamping the individual laminas during the stack formation process.
It is a still further object of the present invention to provide a separation offset between the individual laminas, which offset is recompressed and removed during the final pressing operation in providing the final stack formation of the desired height and having the desired mechanical and electrical properties.